Neuronal and synaptic organization in the gravity receptor system of the statocyst of Octopus vulgaris

Summary The optic tectum of Calamoichthys calabaricus (Polypteriformes) shows a relatively complex vertical stratification, with six main layers and a varied neuronal typology. In particular, pyriform neurons in the well developed stratum griseum periventriculare and some multipolar neurons in the stratum griseum profundum represent the efferent elements of the tectum, while the optic and lemniscal inputs to the tectum converge in the plexiform sublayers of the stratum fibrosum et griseum superficiale. In the circuitry of the tectum some modulation is achieved by some of the polymorphic cells of the stratum griseum internum and by the horizontal cells of the outer layers. Notwithstanding some differences with respect to the teleost optic lobe (i.e., the absence of a torus longitudinalis; the lack of a stratum fibrosum marginale; the modest size of the stratum fibrosum profundum; the paucity of neurons in the stratum fibrosum et griseum superficiale; and the ill-defined separation of the layers of the afferent and efferent fibers), the optic tectum of Calamoichthys resembles the mesotectal type characteristic of teleosts, anurans and reptiles. It exhibits higher degree of organization than the optic tectum of the Chondrostei.     

The synaptic distribution of the retinal input in the superficial layers of the guinea-pig superior colliculus

An evoked potential consisting of four postsynaptic components was recorded in the guinea-pig superior colliculus following electrical stimulation of the contralateral optic nerve. This potential was generated in response to the activation of four populations of optic nerve fibres with different conduction velocities. Current source-density analysis revealed that the two slower conducting fibre populations synapse in the upper third of the stratum griseum superficiale on dendrites whose cell bodies appear to be found in the lower part of this layer and in the stratum opticum. The two faster conducting populations synapse deeper, near the border of the stratum griseum superficiale and stratum opticum, on neurons with cell bodies that may lie towards the upper part of the stratum griseum superficiale. The locations of these postsynaptic sites correspond to the layers in which the optic nerve terminates as revealed by neuroanatomical tracing techniques. Furthermore, neurons of the shape and orientation predicted by the current source-density analysis were found in the superficial layers by using the Golgi-Cox technique.     

墨龙与红鲫的视网膜和视盖解剖结构比较

墨龙是一种由红鲫进化来的龙睛种金鱼(Carassius auratus)。随机取体长10—12 cm, 重约35 g的墨龙和红鲫各4尾, 解剖取出整个眼球及脑, 并常规石蜡切片, HE染色。在光学显微镜下观察墨龙和红鲫的视网膜、视盖系统的显微结构变化并比较各层厚度, 发现与红鲫相比, 墨龙视网膜的总厚度下降29.9%, 其中外网状层厚度增加2.5%、内网状层厚度增加11.8%; 而内核层厚度下降21.6%、外核层厚度降低35.6%, 神经节细胞层、杆锥层也变薄, 且后两者分层不规则; 墨龙视盖壁整体厚度增加28.9%, 其中除围脑室层厚度减少22.6%外, 中央纤维层厚度增加12.8%, 中央细胞层厚度增加30.6%, 表面纤维层厚度增加21.9%, 且纤维远较红鲫密集, 视神经层厚度增加91.7%, 边缘层厚度增加35.6%。结果表明长期的人工选择不但改变了墨龙的外形, 而且使其中枢神经组织结构也发生了较大变化, 并推测墨龙的眼球直径及视网膜面积较大, 从而导致自视网膜传入视盖的纤维增多, 是视网膜和视盖中的传递神经冲动的神经元、神经纤维所在层段增厚的主要原因; 同时墨龙视网膜中色素上皮层向杆锥层交错对插, 富含神经元的视网膜外核层、内核层以及视盖中的围脑室层厚度也降低, 可以减少因视网膜面积大而造成的强光伤害; 此外由于墨龙的围脑室层厚度降低, 导致其游动及平衡能力较红鲫差。     

Interactions between tectal radial cells in the red-eared turtle, Pseudemys scripta elegans: an analysis of tectal modules.

The optic tectum is a major subdivision of the visual system in reptiles. Previous studies have characterized the laminar pattern, the neuronal populations, and the afferent and efferent connections of the optic tectum in a variety of reptiles. However, little is known about the interactions that occur between neurons within the tectum. This study describes two kinds of interactions that occur between one major class of neurons, the radial cells, in the optic tectum of Pseudemys using Nissl, Golgi and electron microscopic preparations. Radial cells have somata which bear long, radially oriented apical dendrites from their upper poles and short, basal dendrites from their lower poles. They are divided into two populations on the basis of the distribution of their somata in the tectum. Deep radial cells have somata densely packed in the stratum griseum periventriculare. Their plasma membranes form casual appositions. Middle radial cells have somata scattered throughout the stratum griseum centrale and stratum fibrosum et griseum superficiale and do not contact each other. The apical dendrites of both populations of radial cells participate in vertically oriented, dendritic bundles. The plasma membranes of the dendrites in these bundles form casual appositions in the deeper tectal layers and chemical, dendrodenritic synapses within the stratum fibrosum et griseum superficiale. The synapses have clear, round synaptic vesicles and slightly asymmetric membrane densities. Thus, radial cells interact via both casual appositions and chemical synapses. These interactions suggest that radial cells may form a basic framework in the tectum. Because both populations of radial cells extend into the stratum fibrosum et griseum superficiale and stratum opticum, they may receive input from some of the same tectal afferent systems. Because the deep radial cells alone have somata and dendrites in the deep tectal layers, they may receive additional inputs that the middle radial cells do not. Neurons in the two populations interact via chemical dendrodentritic synapses, thereby forming vertically oriented modules in the tectum.     

Retinal projections in the catfish,Mystus vittatus (Bloch) as revealed by tracer studies with horseradish peroxidase

Summary The retinal efferents of the catfish, Mystus vittatus, were investigated with the use of the horseradish peroxidase (HRP) technique. Most retinal fibres extended contralateral to the eye that had received HRP label, while a few fascicles projected to the ipsilateral side without decussation in the optic chiasma. The contralateral fibres projected to the suprachiasmatic nucleus, the nucleus opticus dorsolateralis, the nucleus of the posterior commissure, the nucleus geniculatus lateralis, pretectal nuclear complex, and to two layers of the optic tectum, i.e., stratum fibrosum et griseum superficiale and stratum griseum centrale. The accessory optic tract arose from the inner area of the optic tract and extended ventromedially to the accessory optic nucleus. The ipsilateral fascicles projected to almost all the above mentioned nuclei, but these projections were comparatively sparse. The ipsilateral retinal projection was restricted to the rostral tectum.     

Distribution of calbindinlike immunoreactive structures in the optic tectum of normal and eye-enucleated cyprinid fish

Summary Using the ABC immunohistochemical method, we investigated the distribution of calbindinlike immunoreactive structures in the optic tectum of normal fish, Tinca tinca, and from normal and unilaterally eye-enucleated fish, Cyprinus carpio. In nonoperated individuals of both species the optic tectum contained numerous immunoreactive neurons with strongly positive somata located in the stratum periventriculare and a thick immunolabeled dendritic shaft ascending radially toward the stratum fibrosum et griseum superficiale. The retinorecipient layers contained many fibrous immunoreactive structures. Some varicose fibers, isolated or in small bundles, were localized to the stratum album centrale, especially in the dorsal tectal half. Unilateral eye removal produced the disappearance of the immunoreactive fibrous structures located in the retinorecipient layers of the tectum contralateral to the enucleation. The present work shows that calbindinlike immunoreactive substances are localized in specific neural circuits of the fish optic tectum and suggests that the calbindin-like immunoreactive fibers in the retinorecipient strata are of retinal origin.     

Retinal projections in the chain pickerel (Esox niger Lesueur)

Summary The retinal projections inEsox niger, as determined with the aid of a modified cobalt-lysine method, are considerably more extensive in the diencephalon and pretectum than in other teleost fishes so far examined. Although most retinal axons terminate contralaterally, rare fibers can be traced to the same aggregates ipsilaterally. The retinohypothalamic projection appears larger than hitherto reported in teleosts, and the dorsomedial optic tract issues fibers to a series of cell clusters extending from the rostral thalamus to mid-torus levels. A retinal projection to a presumed ventrolateral optic nucleus (VLO) is described for the first time in a teleost. Other targets of retinal fibers include the nucleus geniculatus lateralis ipse of Meader (GLI), the pretectal nucleus (P), the cortical nucleus and a well-developed ventromedial optic nucleus (VMO). The projection to the optic tectum is principally to the stratum fibrosum et griseum superficiale (SFGS) and stratum marginale (SM), but a considerable number of axons also course through the stratum album centrale (SAC) before terminating there or piercing the stratum griseum centrale (SGC) and terminating in SFGS. Rare terminal arborizations of retinal fibers were also observed in stratum griseum centrale (SGS) and in the stratum griseum periventriculare (SGC) in restricted portions of the tectum. Because of the relatively large size of the visual structures inE. niger it is a potentially useful model for future experimental studies on the visual system.     

A crossed projection from the optic tectum to craniocervical premotor areas in the brainstem reticular formation. An anterograde and retrograde tracing study in the mallard (Anas platyrhynchos L.)

The optic tectum in birds receives visual information from the contralateral retina. This information is passed through to other brain areas via the deep layers of the optic tectum. In the present study the crossed tectobulbar pathway is described in detail. This pathway forms the connection between the optic tectum and the premotor area of craniocervical muscles in the contralateral paramedian reticular formation. It originates predominantly from neurons in the ventromedial part of stratum griseum centrale and to a lesser extent from stratum album centrale. The fibers leave the tectum as a horizontal fiber bundle, and cross the midline through the caudal radix oculomotorius and rostral nucleus oculomotorius. On the contralateral side fibers turn to ventral and descend caudally in the contralateral paramedian reticular formation to the level of the obex. Labeled terminals are found in the ipsilateral medial mesencephalic reticular formation lateral to the radix and motor nucleus of the oculomotor nerve, and in the contralateral paramedian reticular formation, along the descending tract. Neurons in the medial mesencephalic reticular formation in turn project to the paramedian reticular formation. Through the crossed tectobulbar pathway visual information can influence the activity of craniocervical muscles via reticular premotor neurons.     

中华蟾蜍中脑组织学研究

采用HE染色和Holmes银染法对蟾蜍中脑的显微结构进行了研究.中脑背侧,视叶可分为顶盖和被盖,顶盖从外侧到内侧依次分为:带状层、外灰质层、浅白质层、中灰质层、中白质层、深灰质层、深白质层和中央灰质.被盖前端分层与顶盖相同,后端分层不明显.中脑腹侧包括被盖和大脑脚,HE染色和Holmes银染法显示,大脑脚从外向内颜色由浅变深,存在大量纵向神经纤维束,两脚底分界处有横向交错的神经纤维.被盖外侧细胞不分层,聚集形成核团.被盖内侧,细胞和纤维以中脑水管为中心,呈同心圆环分8层.通过比较蟾蜍中脑背腹差异程度,了解背腹功能不同.同时对中华蟾蜍中脑同其他脊椎动物的进行了比较.     

Distribution of MAP1A,MAP1B,and MAP2A&;B during layer formation in the optic tectum of developing chick embryos

The expression patterns of three microtubule-associated proteins (MAP1A, MAP1B, and MAP2A&B) were investigated in the developing optic tectum. Expression of MAP1B and middle-molecular-weight peptide of neurofilament (NF-M) was first observed in the same mesencephalic cells on day 3 of incubation, indicating that neuroblasts had been produced. At day 5, MAP1A and MAP2A&B expression appeared in the cellular layer containing the first neuroblasts that differentiate into large multipolar cells. The NF-M⁺ neurites in the striatum album centrale (SAC) and the striatum opticum (SO) were MAP1B⁺ up to day 19, but the intensity of MAP1B immunoreactivity decreased with development. All three MAPs were expressed in large multipolar neurons in the developing stratum griseum centrale from the beginning of maturation. Stratum griseum et fibrosum centrale cellular layers, containing radially arranged piriform neurons, were MAP1A^–/MAP2A&B^– on day 11 but became MAP1A⁺/MAP2A&B⁺ during later stages. These results suggest that the timing of MAP expression in neuronal maturation of large multipolar cells differs from that of piriform cells. The expression of MAPs has revealed specific cellular events in the developing optic tectum. Based on our observations, the development of the optic tectum can be divided into four periods.     

Neurons with complex receptive fields in the stratum griseum centrale of the zebra finch (Taeniopygia guttata castanotis Gould) optic tectum

The electrophysiological and morphological features of visually driven neurons of the stratum griseum centrale of the zebra finch optic tectum were studied by extracellular recording and staining techniques. Stratum griseum centrale neuron responses are sustained in most cases. Receptive fields are big, up to 150 degrees of the visual field. The excitatory center (hot spot) varies in size from 1 degrees to 15 degrees. It can be mapped by small static stimuli, adapts slower than the surround, and has a shape comparable to the excitatory fields of upper-layer neurons. In contrast, the big surround shows responses only to small moving objects which elicit a typical pattern of alternating bursts and silent periods. Alternatively, the same stimuli elicit long-lasting bursts followed by strong adaption. Anatomically, stratum griseum centrale neurons are characterized by far reaching dendrites which terminate with "bottlebrush"-like endings in the upper retinorecipient layers. In addition, they are connected with retinorecipient structures by an interneuron located between layers 10 and 11. The role of the structure of inputs for the organization of the receptive fields is discussed.     

Distribution of an endogenous lectin in the developing chick optic tectum

We determined the cellular localization of an endogenous lectin at various times during the development of a well-characterized region of chick brain, the optic tectum. This lectin is a carbohydrate-binding protein that interacts with lactose and other saccharides, undergoes striking changes in specific activity with development, and has previously been purified by affinity chromatography from extracts of embryonic chick brain and muscle. Cellular localization in the tectum was done by indirect immunofluoresecent staining, using immunoglobulin G derived from an antiserum raised against pure lectin. No lectin was detectable in the optic tectum examined at 5 days of embryonic development. From approximately 7 days of development, neuronal cell bodies and fibers were labeled by the antibody; and extracts of tectum contained hemagglutination activity that could be inhibited by lactose or by the antiserum. Lectin remained present in many tectal neuronal layers after hatching; but in 2-month-old chicks it was sparse or absent in most of the tectum except for prominent labeling of fibers in the stratum album centrale. The initial appearance of lectin in the optic tectum was not dependent on innervation by optic nerve fibers since bilateral enucleation during embryogenesis did not affect it. Lectin was detectable on the surface of embryonic optic tectal neurons dissociated with a buffer containing EDTA.     

Neurophysiological properties of magnetic cells in the pigeon's visual system

Summary Single unit electrical activity was recorded extracellularly in the nucleus of the basal optic root (nBOR) and in the optic tectum under earth-strength magnetic stimulation. Units in the nBOR which were stimulated while the eyes were illuminated by light of different wavelengths exhibited peaks of magnetic responsiveness at 503 nm and 582 nm.Magnetically directional selective cells were found in the stratum griseum et fibrosum superficiale of the optic tectum. They also showed directional selectivity to dynamic photic stimuli. Response peaks varied with the orientation of the pigeon in the horizontal plane. This confirmed that the magnetic responses contained directional information. The results suggest that the receptor and neural organisation of the pigeon's visual system provides an adequate substrate for the detection and elaboration of magnetic compass information.     

IL-1α、IFN-γ、TNF-α和NGF-β在胚胎后期皖西白鹅中脑的表达

用免疫组化SABC法研究白介素-1α(IL-1α)、干扰素-γ(IFN-γ)、肿瘤坏死因子-α(TNF-α)和神经生长因子-β(NGF-β)在胚胎后期皖西白鹅中脑的表达与分布,并作统计学处理。结果发现,中央灰质层、中央白质层、室周灰质纤维层、半圆丘、峡核细胞胞质与突起阳性反应明显,其中峡核阳性反应最为明显,顶盖最不明显,且峡核大细胞部纤维着色明显;IL-1α在4种细胞因子中分布范围最广,阳性反应最强;IFN-γ与TNF-α阳性反应中,部分树突着色明显,且IFN-γ染色效果强于TNF-α;NGF-β的阳性突起与纤维较少。由结果可得,细胞因子可能是通过峡核-顶盖通路的作用,由峡核传递到顶盖;IL-1α在中枢神经系统中有重要作用;IFN-γ作为中枢神经系统介质的作用强于TNF-α。     

Acetylcholinesterase activity in the normal and retino-deprived optic tectum of the quail

Summary Acetylcholinesterase localization has been studied by electron microscopic histochemistry in the quail optic tectum. Ultrastructural analysis reveals that the different neuronal types in the tectum possess the metabolic pathways for AChE synthesis to different degrees. From the site of synthesis in cell bodies the enzyme spreads towards areas of neuropil. In the neuropil of AChE-rich areas a balance seems to exist between enzyme stored in dendrites (and sometimes axon terminals) and enzyme released into the extracellular spaces. Precise identification of cholinergic synapses by means of AChE localization is in most cases impossible, due to extensive spread of the enzyme through the extracellular compartments of the neuropil.Unilateral ocular ablation causes disappearance of the stratum opticum and decrease in thickness of the superficial tectal layers in the contralateral optic tectum, but only minor modifications in AChE localization. This finding is in agreement with biochemical results which show equivalence of the relative concentration of AChE in the right and left optic tectum 1 or 2 months after ablation of the right eye. The experimental evidence suggests that cholinergic mechanisms are not related to the discharge of retinal afferents on receptive tectal neurons, but more likely to intrinsic neural circuits which might be involved in the modulation of tectal activity.     

TOPOGRAPHICAL AND SUBCELLULAR DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE AND GLUTAMATE DECARBOXYLASE IN PIGEON OPTIC TECTUM

Abstract— The distribution of choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) in different layers of the pigeon optic tectum and in some nuclei of the optic lobe have been investigated. About 40% of GAD and 25% of ChAT were found in the superficial part of tectum, but negligible activity was found in the stratum opticum. The highest GAD activity was found in layers 3-7 (according to the nomenclature of C ajal , 1911) with a peak in layer 4. ChAT activity peaked in layers 3, 5. 8 and 10/11. Its distribution correlated well with the staining pattern of AChE, particularly in the superficial part of the tectum. The distribution of ChAT and GAD did not change significantly 4 weeks after enucleation. ChAT and GAD activities were high in the nucleus isthmi, pars parvocellularis (Ipc). The activity of GAD was also high in the nucleus intercollicularis (ICo), the other nuclei showed less activity of both enzymes.     

北草蜥中脑视叶组织学结构观察

用光学显微镜对北草蜥(Takydromus septentrionalis)中脑视叶组织学结构进行了观察。视叶分为背侧的顶盖和腹侧的被盖,两者无明显界限。顶盖处灰质和白质交替排列。由表及里,可分为分子层、外灰质层、浅白质层、中灰质层、中白质层、深灰质层、深白质层和室管膜层。被盖处细胞层次不明显。在视叶的前部有横行的纤维将左右视叶联系起来。左右视叶室与中脑水管以及两视叶间的纵沟在视叶的中、后部相通。同时将北草蜥的中脑与其它低等脊椎动物进行了比较,推测北草蜥在进化上处于较低等地位。     

Brain-derived neurotrophic factor (BDNF)-like immunoreactivity localization in the retina and brain of Cichlasoma dimerus (Teleostei, Perciformes)

Brain-derived neurotrophic factor (BDNF) is a neurotrophin involved in the development and maintenance of vertebrate nervous systems. Although there were several studies in classical animal models, scarce information for fish was available. The main purpose of this study was to analyze the distribution of BDNF in the brain and retina of the cichlid fish Cichlasoma dimerus. By immunohistochemistry we detected BDNF-like immunoreactive cells in the cytoplasm and the nuclei of the ganglion cell layer and the inner nuclear layer of the retina. In the optic tectum, BDNF-like immunoreactivity was detected in the nucleus of neurons of the stratum periventriculare and the stratum marginale and in neurons of the intermediate layers. In the hypothalamus we found BDNF-like immunoreactivity mainly in the cytoplasm of the nucleus lateralis tuberis and the nucleus of the lateral recess. To confirm the nuclear and cytoplasm localization of BDNF we performed subcellular fractionation, followed by Western blot, detecting a 39 kDa immunoreactive-band corresponding to a possible precursor form of BDNF in both fractions. BDNF-like immunoreactivity was distributed in areas related with photoreception (retina), the integration center of retinal projections (optic tectum) and the control center of background and stress adaptation (hypothalamus). These results provide baseline anatomical information for future research about the role of neurotrophins in the adult fish central nervous system.     

Projections of the optic tectum and the mesencephalic nucleus of the trigeminal nerve in the tegu lizard (Tupinambis nigropunctatus)

Summary Fibers undergoing Wallerian degeneration following tectal lesions were demonstrated with the Nauta and Fink-Heimer methods and traced to their termination. Four of the five distinct fiber paths originating in the optic tectum appear related to vision, while one is related to the mesencephalic nucleus of the trigeminus. The latter component of the tectal efferents distributes fibers to 1) the main sensory nucleus of the trigeminus, 2) the motor nucleus of the trigeminus, 3) the nucleus of tractus solitarius, and 4) the intermediate gray of the cervical spinal cord.The principal ascending bundle projects to the nucleus rotundus, three components of the ventral geniculate nucleus and the nucleus ventromedialis anterior ipsilaterally, before it crosses in the supraoptic commissure and terminates in the contralateral nucleus rotundus, ventral geniculate nucleus and a hitherto unnamed region dorsal to the nucleus of the posterior accessory optic tract.Fibers leaving the tectum dorso-medially terminate in the posterodorsal nucleus ipsilaterally and the stratum griseum periventriculare of the contralateral tectum. The descending fiber paths terminate in medial reticular cell groups and the rostral spinal cord contralaterally and in the torus and the lateral reticular regions ipsilaterally. The ipsilateral fascicle also issues fibers to the magnocellular nucleus isthmi.     

Neurolin, a cell surface glycoprotein on growing retinal axons in the goldfish visual system, is reexpressed during retinal axonal regeneration.

The mAb E 21 recognizes a cell surface glycoprotein selectively associated with fish retinal ganglion cell axons that are in a state of growth. All retinal axons and ganglion cells in goldfish embryos stained for E 21. In adult fish, however, E 21 immunoreactivity exhibited a patterned distribution in ganglion cells in the marginal growth zone of the continuously enlarging fish retina and the new axons emerging from these cells in the retina, optic nerve, and optic tract. The E 21 antigen was absent from older axons, except the terminal arbor layer in the tectum, the Stratum fibrosum et griseum superficiale where it was uniformly distributed. Upon optic nerve transection, the previously unlabeled axons reacquired E 21 positivity as they regenerated throughout their path to the tectum. Several months after ONS, however, E 21 staining disappeared from the regenerated axons over most of their lengths but reappeared as in normal fish in the terminal arbor layer. The immunoaffinity-purified E 21 antigen, called Neurolin, has an apparent molecular mass of 86 kD and contains the HNK1/L2 carbohydrate moiety, like several members of the class of cell adhesion molecules of the Ig superfamily. The NH2-terminal amino acid sequence has homologies to the cell adhesion molecule DM-Grasp recently described in the chicken. Thus, retinal ganglion cell axons express Neurolin during their development and are able to reexpress this candidate cell adhesion molecule during axonal regeneration, suggesting that Neurolin is functionally important for fish retinal axon growth.